System and method including multi-circuit solution extraction for recovery of metal values from metal-bearing materials

ABSTRACT

The present disclosure relates to a metal recovery process comprising a solvent extraction process. In an exemplary embodiment, the solution extraction system comprises a plant with a first and second circuit. A high-grade pregnant leach solution (“HGPLS”) is provided to the first and second circuit, and a low-grade pregnant leach solution (“LGPLS”) is provided to the second circuit. The first circuit produces a rich electrolyte, which can be forwarded to a primary metal recovery, and a low-grade raffinate, which can be forwarded to a secondary metal recovery process. The second circuit produces a rich electrolyte, which can also be forwarded to the primary metal recovery process. The first and second circuits are in fluid communication with each other.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of and claims priority toU.S. patent application Ser. No. 16/671,323, entitled “SYSTEM AND METHODINCLUDING MULTI-CIRCUIT SOLUTION EXTRACTION FOR RECOVERY OF METAL VALUESFROM METAL-BEARING MATERIALS,” which was filed on Nov. 1, 2019 (the“'323 Application). The '323 Application is a continuation of and claimspriority to U.S. patent application Ser. No. 16/020,405, entitled“SYSTEM AND METHOD INCLUDING MULTI-CIRCUIT SOLUTION EXTRACTION FORRECOVERY OF METAL VALUES FROM METAL-BEARING MATERIALS,” which was filedon Jun. 27, 2018, now U.S. Pat. No. 10,501,821, issued Dec. 10, 2019(the “'405 Application). The '405 application is a continuationapplication of and claims priority to U.S. patent application Ser. No.14/920,768, entitled “SYSTEM AND METHOD INCLUDING MULTI-CIRCUIT SOLUTIONEXTRACTION FOR RECOVERY OF METAL VALUES FROM METAL-BEARING MATERIALS,”which was filed on Oct. 22, 2015, now U.S. Pat. No. 10,036,080, issuedJul. 31, 2018 (the '768 Application). The '768 Application is adivisional application of and claims priority to U.S. patent applicationSer. No. 13/331,717, entitled “SYSTEM AND METHOD INCLUDING MULTI-CIRCUITSOLUTION EXTRACTION FOR RECOVERY OF METAL VALUES FROM METAL-BEARINGMATERIALS,” which was filed on Dec. 20, 2011, now U.S. Pat. No.9,169,533, issued Oct. 27, 2015. The aforementioned applications arehereby incorporated by reference herein in their entireties.

FIELD OF THE INVENTION

The invention relates generally to systems and methods for extraction ofmetal values from metal-bearing materials, and more specifically, tosystems and methods for recovering metal values using solutionextraction techniques.

BACKGROUND OF THE INVENTION

Hydrometallurgical treatment of metal-bearing materials, such as metalores, metal-bearing concentrates, and other metal-bearing substances,has been well established for many years. Moreover, leaching ofmetal-bearing materials is a fundamental process utilized to extractmetal value from metal-bearing materials. Typical leach processescomprise contacting a metal-bearing material with an aqueous solutioncontaining a leaching agent which extracts the metal or metals from themetal-bearing material into solution. For example, in copper leachingoperations, especially copper from copper minerals, such as chalcopyriteand chalcocite, aqueous sulfuric acid is contacted with a copper-bearingore. During the leaching process, acid in the leach solution may beconsumed and various soluble components are dissolved thereby increasingthe metal content of the aqueous solution.

The aqueous leach solution containing the leached metal can then betreated by, for example, solution extraction, wherein the aqueous leachsolution is contacted with an organic solution comprising ametal-specific extraction reagent, for example, an aldoxime and/orketoxime, to form an aqueous phase and an organic phase. Themetal-specific extraction reagent extracts the metal from the aqueousphase into the organic phase. During a solution extraction process forcopper and certain other metals, a leaching agent may be regenerated inthe aqueous phase. For example, when sulfuric acid is used as theleaching agent, sulfuric acid can be regenerated in the aqueous phasewhen copper is extracted into the organic phase by the extractionreagent.

After copper is removed from the aqueous phase into the organic phase,the diluted aqueous solution, now called the raffinate, may be recycledback to the leaching process, recycled to the front of a solid-liquidseparation process, and/or forwarded to secondary metal extractionprocesses, such as, for example, cobalt recovery.

Numerous technical challenges exist with typical leaching and solventextraction processes. For example, under current leaching and solutionextraction processes, large concentrations of soluble metal and metalprecipitate can be lost in the metal-depleted, acid-containing aqueousphase raffinate solutions. These losses lead to inefficiencies andrelatively low overall process yields. Additionally, relatively highprimary metal concentrations (such as copper) in the raffinate makerecovery of secondary metals costly and possibly impractical.

Accordingly, systems and methods for more easily controlling processconditions, such as the concentration of a primary metal the raffinatesolution, would be advantageous. Additionally, systems and methods forimproved recovery of secondary metals from a raffinate solution aredesirable.

SUMMARY OF THE INVENTION

The present invention generally relates to a system and method forrecovery of metal values from metal-bearing materials using solventextraction techniques. The system and method employ a solvent extractionplant that includes a first circuit and a second circuit in fluidcommunication. As set forth in more detail below, various advantages ofthe system and method of the present disclosure include improved primarymetal recovery, improved secondary metal recovery, and/or improved plantutilization.

An exemplary method for extracting one or more metal values from ametal-bearing solution comprises providing a first portion of a firstmetal-bearing solution to a first circuit of a solution extractionplant, providing a second portion of the first metal-bearing solution toa second circuit of the solution extraction plant, wherein the firstcircuit of the solution extraction plant and the second circuit of thesolution extraction plant are in fluid communication with each other,providing a second metal-bearing solution to the second circuit of thesolution extraction plant, extracting a first circuit raffinate,extracting a first circuit electrolyte, and extracting a second circuitelectrolyte. The first circuit raffinate may comprise a low-graderaffinate. In accordance with various aspects of these embodiments, thefirst circuit and the second circuit are fluidly coupled by coupling anoutput of a first extractor of the second circuit to an input of a firstextractor of the first circuit. Additionally, an output of a secondextractor of the second circuit may be coupled to an input of a secondextractor of the first circuit. In this case, a low-grade raffinate canbe extracted from the first extractor of the first circuit, a high-graderaffinate can be extracted from the second extractor of the firstcircuit, and another high-grade raffinate can be extracted from a thirdextractor of the first circuit. In accordance with further aspects, leanelectrolyte is provided to a stripper of the first circuit.

An exemplary system for extracting one or more metal values from ametal-bearing material comprises a first metal-bearing solution, asecond metal-bearing solution, a solution extraction plant comprising afirst circuit and a second circuit, wherein the first circuit comprisesat least two first circuit extractors and at least one first circuitstripping unit, the second circuit comprises at least two second circuitextractors and at least one second circuit stripping unit, and the firstcircuit and second circuit are in fluid communication with each other. Asecond circuit raffinate may be produced by the second circuit andprovided to one of the first circuit extractors. In accordance withadditional aspects of these embodiments, the first circuit additionallyinvolves a third extractor and a fourth extractor, and a secondstripping unit.

In accordance with additional embodiments of the invention, an exemplaryprocess for recovering one or more metals from a metal-bearing materialcomprises preparing a metal-bearing material, performing a reactiveprocess on the metal-bearing material, extracting metal value from theprocessed metal-bearing material using the solution extraction methoddescribed herein, and subjecting extracted the metal value to at leastone metal recovery step, such as electrowinning. In accordance withvarious aspects of these embodiments, the solution extraction methodinvolves the use of a solution extraction plant comprising a firstcircuit and second circuit. The first circuit and the second circuit arefluidly coupled by coupling an output of a first extractor of the secondcircuit to an input of a first extractor of the first circuit.Additionally, an output of a second extractor of the second circuit maybe coupled to an input of a second extractor of the first circuit. Inthis case, a low-grade raffinate can be extracted from the firstextractor of the first circuit, a high-grade raffinate can be extractedfrom the second extractor of the first circuit, and another high-graderaffinate can be extracted from a third extractor of the first circuit.In accordance with further aspects, a lean electrolyte is provided to astripper of the first circuit.

An exemplary system for recovering one or more metals from ametal-bearing material comprises a grinding unit, a leach system, one ormore solid-liquid separators, a solution extraction plant with a firstcircuit and a second circuit as described herein, and at least oneelectrowinning operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements and wherein:

FIG. 1 illustrates a flow diagram of a metal recovery process inaccordance with exemplary embodiments of the invention;

FIG. 2 illustrates a flow diagram of a solution extraction step of ametal recovery process in accordance with exemplary embodiments of theinvention;

FIG. 3 illustrates a flow diagram of a solution extraction system inaccordance with an exemplary embodiment of the invention;

FIG. 4 illustrates a flow diagram of a solution extraction system inaccordance with another exemplary embodiment of the invention; and

FIG. 5 illustrates a flow diagram of a solution extraction system inaccordance with yet another exemplary embodiment of the invention.

DETAILED DESCRIPTION

The detailed description of various embodiments herein makes referenceto the accompanying drawing figures, which show various embodiments andimplementations thereof by way of illustration, and not of limitation.While these embodiments are described in sufficient detail to enablethose skilled in the art to practice the embodiments, it should beunderstood that other embodiments may be realized and that mechanicaland other changes may be made without departing from the spirit andscope of the present disclosure. Furthermore, any reference to singularincludes plural embodiments, and any reference to more than onecomponent may include a singular embodiment.

A system and method of various exemplary embodiments of the presentinvention exhibit significant advancements over prior art processes,particularly with regard to metal recovery and process efficiency.Moreover, existing metal recovery systems and processes that utilize areactive process and solution extraction for metal recovery may, in manyinstances, be easily retrofitted to exploit the many commercial benefitsof the present invention.

In various exemplary embodiments, a metal recovery process comprisespreparing a metal-bearing material, performing a reactive process on themetal-bearing material, extracting metal value from the processedmetal-bearing material, and subjecting the extracted metal value to atleast one metal recovery step, such as electrowinning.

FIG. 1 illustrates an exemplary metal recovery process 100 forrecovering a metal from a metal-bearing material 101, including thesteps of preparing metal-bearing material step 10, reactive processingstep 20, optional conditioning step 30, solution extraction step 40,primary metal recovery step 50 and optional secondary metal recoverystep 60. In various exemplary embodiments, metal recovery process 100 isconfigured to recover multiple metal values from metal-bearing material101. For example, metal recovery process 100 may be configured torecover a primary and a secondary metal, such as cobalt, from an oreand/or concentrate comprising a significant concentration of the primarymetal.

Metal-bearing material 101 may be an ore, a concentrate, or any othermaterial from which valuable and/or useful metal values may berecovered. Such metal values may include, for example, copper, gold,silver, zinc, platinum group metals, nickel, cobalt, molybdenum,rhenium, uranium, rare earth metals, and the like. By way of a specificexample, metal recovery process 100 is configured to recover copper fromcopper-bearing material, such as, for example, ores and/or concentratescontaining chalcopyrite (CuFeS₂), chalcocite (Cu₂S), bornite (Cu₅FeS₄),and covellite (CuS), malachite (Cu₂CO₃(OH)₂), pseudomalachite(Cu₅[(OH)₂PO_(4]2)), azurite (Cu₃(CO₃)₂(OH)₂), chrysocolla((Cu,Al)₂H₂Si₂O₅(OH)₄.nH₂0), cuprite (Cu₂O), brochantite(CuSO₄.3Cu(OH)₂), atacamite (Cu₂[OH₃Cl]) and other copper-bearingminerals or materials and mixtures thereof.

During preparation of metal-bearing material step 10, metal-bearingmaterial 101 is prepared for reactive processing step 20. Metal-bearingmaterial 101 may be prepared in any manner that facilitates the recoveryof metal values from metal-bearing material 101—such as, for example,manipulating a composition and/or component concentration ofmetal-bearing material 101—for the chosen reactive processing method ofstep 20. Desired composition and component concentration parameters canbe achieved through a variety of chemical and/or physical processingstages, the choice of which will depend upon the operating parameters ofthe chosen processing scheme, equipment cost and materialspecifications. For example, metal-bearing material 101 may undergocomminution, flotation, blending, and/or slurry formation, as well aschemical and/or physical conditioning in preparation step 10 beforemetal extraction. Any processing of metal-bearing material 101 whichimproves the ability to recover metal value from the material is inwithin the scope of the present disclosure.

In various exemplary embodiments, step 10 comprises a controlledgrinding step. Controlled grinding may be used to produce a uniformparticle size distribution of metal-bearing material 101. Additionally,liquid, such as process water, may be added to metal-bearing material101 to create a pulp density which corresponds to desirable operatingconditions of the controlled grinding unit. Acceptable techniques anddevices for reducing the particle size of the metal-bearing materialinclude, for example, ball mills, tower mills, grinding mills, attritionmills, stirred mills, horizontal mills and the like, and additionaltechniques may later be developed that may achieve the desired result ofreducing the particle size of the copper-bearing material to betransported.

After metal-bearing material 101 has been suitably prepared for metalrecovery processing, it may be combined with any number of liquid feedstreams to form a metal-bearing inlet stream 103. Preferably, in anexemplary embodiment of the present invention, the liquid feed streamcomprises process water, but any suitable liquid may be employed, suchas, for example, recycled raffinate, pregnant leach solution, leanelectrolyte, and/or other recycled streams from the metal recoveryprocesses, including but not limited to secondary metal, such as cobaltor iron, recovery process streams.

After step 10, metal-bearing inlet stream 103 may be forwarded to areactive processing step 20. Step 20 may comprise any process orreaction which places metal-bearing inlet stream 103 in condition forlater metal recovery processing. Such processes may include, forexample, a leaching step. In such configurations, the leaching step maycomprise atmospheric leaching, ammonia leaching, pressure leaching,whole ore leaching, agitation leaching, heap leaching, stockpileleaching, pad leaching, thin-layer leaching and/or vat leaching, ateither ambient or elevated temperatures, or any suitable process orreaction that puts metal value in metal-bearing inlet stream 103 in acondition such that it may be subjected to later metal recoveryprocessing, is within the scope of the present disclosure.

During step 20, the metal value is solubilized or otherwise liberated inpreparation for later recovery processes. Any substance that assists insolubilizing the metal value, and thus releasing the metal value from ametal-bearing material, may be used. For example, where copper is themetal being recovered, an acid, such as sulfuric acid, may be contactedwith the copper-bearing material such that the copper is solubilized forlater recovery steps. However, it should be appreciated that anysuitable method of solubilizing metal value in preparation for latermetal recovery steps is within the scope of the disclosure.

After step 20, the metal-bearing product stream 105 may undergo one ormore optional conditioning steps 30. In an exemplary embodiment, productstream 105 of reactive processing step 20 is conditioned to adjust thecomposition, component concentrations, solids content, volume,temperature, pressure, and/or other physical and/or chemical parametersto desired values. Generally, a properly conditioned metal-bearingproduct stream 105 will contain a relatively high concentration ofsoluble metal, for example, copper sulfate, in an acid solution and maycontain few impurities. Moreover, the conditions of the metal-bearingproduct stream 105 may be kept substantially constant to enhance thequality and uniformity of the copper product ultimately recovered.

By way of example, step 30 may comprise adjusting certain physicalparameters of the product stream 105. Step 30 may comprise, for example,reagent additions, flashing processes, and one or more solid-liquidphase separation steps. For example, in various exemplary embodiments,product stream 105 may be further conditioned in preparation for latermetal value recovery steps by one or more solid-liquid phase separationsteps for the purpose of separating solubilized metal solution fromsolid particles. This may be accomplished in any conventional manner,including use of filtration systems, CCD circuits, thickeners,clarifiers, and the like. A variety of factors, such as the processmaterial balance, environmental regulations, residue composition,economic considerations, and the like, may affect the decision whetherto employ a CCD circuit, a thickener, a filter, a clarifier, or anyother suitable device in a solid-liquid separation apparatus. One ormore solid-liquid phase separation steps may be carried out with aconventional CCD utilizing conventional countercurrent washing of theresidue stream to recover leached metal values to one or more solutionproducts and to minimize the amount of soluble metal values advancingwith the solid residue to further metal recovery processes or storage.

In various exemplary embodiments, step 30 comprises a solid-liquid phaseseparation step to produce a first metal-bearing solution and a secondmetal-bearing solution. In such embodiments, the first metal-bearingsolution comprises a high-grade pregnant leach solution (“HGPLS”) 102,comprising relatively high concentrations of dissolved metal values, andthe second metal-bearing solution comprises a low-grade pregnant leachsolution (“LGPLS”) 106, comprising a lower concentration of dissolvedmetal values than HGPLS 102. While the concentration of a primary metalvalue of both HGPLS and LGPLS may vary on an absolute basis, in variousembodiments, the HGPLS will have a higher concentration of a primarymetal value than the LGPLS. Stated another way, HGPLS and LGPLS maycontain very low, or very high, primary metal value concentrations.

In various exemplary embodiments, large amounts of wash water areutilized in a solid-liquid phase separation step 30. This wash watercollects the remaining dissolved metal values from product stream 105and may become part of LGPLS 106. The separated solids may further besubjected to later processing steps, including other metal recoveryprocesses, such as, for example, recovery of gold, silver, platinumgroup metals, molybdenum, zinc, nickel, cobalt, uranium, rhenium, rareearth metals, and the like, by sulphidation, cyanidation, or othertechniques. Alternatively, the separated solids may be subject toimpoundment or disposal.

In various exemplary embodiments, at least one HGPLS (e.g., solution102) and at least one LGPLS (e.g., solution 106) are forwarded to asolution extraction step 40. Step 40 produces at least one primary metalvalue containing stream 192 and may produce one or more secondary metalvalue containing streams, e.g., low grade raffinate 146. For example, asdiscussed in connection with FIGS. 2 and 3, two HGPLS streams and oneLGPLS stream may be forwarded to solution extraction step 40. In otheraspects, a single HGPLS stream and a single LGPLS stream may be providedto solution extraction step 40.

In many instances, due to variations in concentration and quality of themetal-bearing material 101, it may be advantageous to mix one or moreleach solutions prior to solution extraction to form a firstmetal-bearing solution and/or a second metal-bearing solution.Additionally or alternatively, it may be beneficial to process two ormore separate leach solution streams produced by multiple leachprocesses in a single solution extraction process or system. Forexample, if an operation has both a heap leach operation and a pressureor agitated leach operation, then the heap leach solution, equivalent tothe LGPLS, may need to be processed with a more concentrated pregnantleach solution, such as HGPLS. It is not required that the HGPLS andLGPLS are produced from the same step 20; the HGPLS, LGPLS, or both canbe produced by one or more steps 20. Additionally, multiple steps 30,such as controlled grinding steps, flashing steps, and/or solid-liquidphase separation steps may be utilized to produce the HGPLS and/or theLGPLS.

In various exemplary embodiments, the LGPLS has a concentration of aprimary metal value greater than about 20% of the concentration of theprimary metal value in the HGPLS. Preferably, the LGPLS has aconcentration of the primary metal value greater than about 40% of theconcentration of the primary metal value in the HGPLS. Most preferably,the LGPLS has a concentration of the primary metal value greater thanabout 50% of the concentration of the primary metal value in the HGPLS.

In step 40, at least one raffinate may be produced. The at least oneraffinate can be low-grade raffinate with a relatively low primary metalconcentration and a relatively high secondary metal concentration. Thelow-grade raffinate may be forwarded to secondary metal recoveryprocesses, such as a secondary metal recovery step 60 (which isdiscussed in more detail below). The production of any number and/ortype of raffinate is within the scope of the present disclosure.

With initial reference to FIG. 2, an exemplary solution extractionprocess 200, suitable for step 40, is illustrated. Although individualsteps of process 200 may be described as occurring sequentially, in someinstances, the steps may occur simultaneously, or in a different processorder than described below.

Process 200 includes the steps of providing a first metal-bearingsolution to a first and second solution extraction circuit (step 202),producing a first loaded organic stream (step 204), producing a firstcircuit enriched electrolyte (step 206), producing a first circuitraffinate (step 208), optionally producing additional first circuitraffinates (step 210), providing a second metal-bearing solution to thesecond circuit (step 212), producing a second circuit loaded organicstream and second circuit raffinate (step 214), producing a secondsecond circuit raffinate (step 216), and producing a second circuitenriched electrolyte (step 218).

With initial reference to FIG. 3, in various exemplary embodiments,process 200 is performed using a single solution extraction plant 300comprising a first solution extraction circuit 301 and a second solutionextraction circuit 302. In various embodiments, one or more processstreams are forwarded from the second solution extraction circuit to thefirst solution extraction circuit. In this case, a system and methodprovide, inter alia, efficient and controllable metal solutionextraction from at least two separate pregnant leach solution feedstreams, which may be used to recover two or more recoverable metalvalues. Where two metal values may be recoverable, one metal value maybe referred to as a primary metal value and the other referred to as asecondary metal value.

In the illustrated case, first circuit 301 is configured to receiveHGPLS 102 and lean electrolyte 108 and produce a rich electrolyte 162and one or more raffinates 126, 136, and/or 146. First circuit 301includes at least two extractors and at least one stripping unit. In theillustrated case, first circuit 301 includes four extractors (310, 320,330, and 340) and two stripping units (350 and 360) which are fluidlycoupled together.

Second circuit 302 is configured to receive a HGPLS 104 and a LGPLS 106,and includes at least two extractors and at least one stripping unit. Inthe illustrated case, second circuit includes two extractors (370 and380) and one stripping unit 390 which are fluidly coupled together.However, the use of additional extractors and stripping units in secondcircuit 302 is within the scope of the present disclosure.

With reference to FIG. 2 and FIG. 3, step 202 includes providing a firstmetal-bearing solution to a first circuit and a second circuit. By wayof example, step 202 comprises providing HGPLS 102 to a first circuitextractor 310 of first circuit 301 and HGPLS 104 to a second circuitextractor 370 of second circuit 302. However, in various embodiments,HGPLS 102 may be provided to first circuit 301 and a second HGPLS 104may be provided to second circuit 302. It is not required that HGPLS 102and second HGPLS 104 be equivalent or derived from the same priorreactive processing step or steps 20.

In step 204, a first loaded organic stream 114 is formed by contactingHGPLS 102 with a partially loaded organic stream 118. In suchconfigurations, extractor 310 produces a first loaded organic stream 114and an aqueous stream 116.

In step 206, a first circuit enriched electrolyte 162 is formed bycontacting first loaded organic stream 114 with an intermediateelectrolyte 156, which is aqueous stream comprising a lowerconcentration of primary metal than that of first circuit enrichedelectrolyte 162, in stripping unit 360. Stripping unit 360 furtherproduces a partially stripped organic stream 158, which may be forwardedfor further processing in the first circuit 301.

In such embodiments, intermediate electrolyte 156 is produced by astripping unit 350. Stripping unit 350 is configured to receive a leanelectrolyte 108 and partially stripped organic stream 158 from strippingunit 360. Intermediate electrolyte 156 is formed by contacting leanelectrolyte 108 and partially stripped organic stream 158 in strippingunit 350. Intermediate electrolyte 156 is then forwarded to strippingunit 360.

In step 208, first circuit raffinate 146 is produced by contactingbarren organic stream 148 with second circuit raffinate 186 in extractor340. Barren organic stream 148 comprises a metal-specific extractionreagent, such as, for example, an aldoxime and/or ketoxime, whichextracts a primary metal value from second circuit raffinate 186 intothe organic phase to form a partially loaded organic stream 138 andfirst circuit raffinate 146. Barren organic may be recycled from variousother processes and solution extraction components. As such, the term“barren” means sufficiently low in concentration of a primary metalvalue.

In an aspect of various embodiments, first circuit raffinate 146 is alow-grade raffinate. As will be discussed in greater detail below,low-grade raffinate 146 may be forwarded to further processing forsecondary metal recovery. (e.g., step 60 of process 100).

In step 210, additional extractors may be added to first circuit 301 toproduce at least one additional raffinate. These raffinates may beaqueous solutions with a relatively low primary metal concentration,such as low-grade raffinates, or aqueous solutions with a primary metalconcentration higher than low-grade raffinates, such as high-graderaffinates. The use of any number or configuration of additionalextractors in first circuit 301 is within the scope of the presentdisclosure.

For example, additional extractors 320 and 330 are configured to receivepartially loaded organic streams 128 and 138 and metal-bearing aqueoussolutions, such as 176 and 116. In such embodiments, the partiallyloaded organic streams and aqueous solutions are contacted withinextractors 320 and 330, producing partially loaded organic streams 118and 128 and aqueous high-grade raffinates 126 and 136.

High-grade raffinates 126 and 136 may be used beneficially in a numberof ways. For example, all or a portion of high-grade raffinates 126 and136 may be recycled to step 10. The use of high-grade raffinates 126 and136 in leaching operations may be beneficial because the acid and ferriciron values contained in high-grade raffinates 126 and 136 may optimizethe potential for leaching oxide and/or sulfide ores that commonlydominate many leaching operations. That is, the ferric and acidconcentrations of high-grade raffinates 126 and 136 may be used tooptimize the pH of heap leaching operations. It should be appreciatedthat the properties of high-grade raffinates 126 and 136, such ascomponent concentrations, may be adjusted in accordance with the desireduse high-grade raffinates 126 and 136.

Extractor 330 may be configured to receive a second circuit raffinate176. In such configurations, second circuit raffinate 176 is forwardedto first circuit 301 from second circuit 302. Any number of secondcircuit raffinates may be forwarded from second circuit 302 to firstcircuit 301, provided a first circuit extractor is configured to receivethe second circuit raffinate.

Step 212 provides LGPLS 106 to second circuit 302 (e.g., extractor 380).LGPLS 106 may be provided by step 30 of metal recovery method 100 orfrom other sources. LGPLS 106 may comprise, for example, wash watercollected from prior conditioning steps, such as a solid-phaseseparation and/or a flashing of the slurry. In other aspects, LGPLS 106may comprise the liquid product of a leaching step performed on a lowergrade metal-bearing material than the metal-bearing material used toproduce HGPLS 102 and/or 104. Any LGPLS 106 which includes primary metalvalue and is of a lower concentration than the HGPLS 104 is within thescope of the present disclosure.

In step 214, a second raffinate is provided. In the illustratedembodiment, the second raffinate is produced by contacting HGPLS 104with a partially loaded organic stream 178 in extractor 370 to producesecond loaded organic stream 174 and second circuit raffinate 176.Second circuit raffinate 176 may be provided to an extractor (such asextractor 330) of first circuit 301. However, second circuit raffinate176 may be provided to any component of first circuit 301 which isconfigured to receive the raffinate. In addition, second circuitraffinate 176 may be provided to other processes, as described above inrelation to first circuit raffinates 126 and 136.

In step 216, another second circuit raffinate is formed by contactingLGPLS 106 with barren organic stream 188 in extractor 370 to produce asecond circuit raffinate 186 and a partially loaded organic stream 178.In an aspect of these embodiments, second circuit raffinate 186 may beprovided to an extractor (such as extractor 340) of first circuit 301.However, second circuit raffinate 186 may be provided to any componentof first circuit 301 which is configured to receive the raffinate. Inaddition, second circuit raffinate 186 may be provided to otherprocesses, as described above in relation to first circuit raffinates126 and 136.

When second circuit raffinate 176 or 186 is provided to first circuitextractor 340, extractor 340 may produce a raffinate 146 containing arelatively low concentration of primary metal. This occurs becauseraffinate 146 is produced by contacting an aqueous stream with a barrenorganic stream in two consecutive stages. For example, in FIG. 3,raffinate 146 is formed by contacting LGPLS 106 with barren organicstream 188 in second circuit extractor 380. The resulting aqueous stream(e.g., second circuit raffinate 186) is then contacted with barrenorganic stream 148 in first circuit extractor 340. This double exposureto barren organic, which is very low in primary metal concentration,produces a raffinate 146 which has a very low concentration of primarymetal. Raffinate 146 is therefore well suited to secondary metalrecovery step 60.

In the case where an aqueous stream is forwarded from second circuit 302to first circuit 301 to produce a raffinate low in primary metal value,the operating conditions of second circuit 302 significantly impact thequality of the raffinate. For example, as illustrated in FIG. 3, theconcentration of primary metal value in raffinate 146 is dependent uponthe concentration of primary metal value in second circuit raffinate186. In such configurations, it may be desirable to control the processconditions such that second circuit raffinate 186 is low in primarymetal value concentration.

With continued reference to FIG. 2, in step 218, second circuit enrichedelectrolyte 192 is formed by, for example, contacting second loadedorganic stream 174 with an aqueous solution in stripping unit 390. In anaspect of these embodiments, the aqueous solution comprises leanelectrolyte 112. However, the use of any aqueous solution having aprimary metal concentration lower than second circuit enrichedelectrolyte 192 is within the scope of the present disclosure.

Second circuit enriched electrolyte stream 192 may be combined withfirst circuit enriched electrolyte stream 162. The combined richelectrolyte may be forwarded to primary metal value recovery processes(e.g., step 50 of process 100). In other embodiments, second circuitenriched electrolyte stream 192 is not combined with first circuitenriched electrolyte stream 162, and may be processed independently. Inyet other embodiments, either or both of first circuit enrichedelectrolyte stream 162 and second circuit enriched electrolyte stream192 may be sent to an electrolyte recycle tank. The electrolyte recycletank may suitably facilitate process control for an electrowinningcircuit, as will be discussed in greater detail below.

The particular embodiment described in connection with FIG. 3 merelyillustrates an exemplary system for solution extraction in accordancewith the present disclosure. Various other exemplary embodimentscomprise multiple stripping units and extractors arranged in series,parallel, and/or split configurations. For example, various exemplaryembodiments may utilize a first circuit and/or second circuit withadditional or fewer stripping units and/or extractors than first circuit301 and/or second circuit 302. Additional exemplary embodiments arediscussed in further detail below. The use of any suitable number ofstripping units and extractors, in any suitable configuration, is withinthe scope of the present disclosure.

With initial reference to FIG. 4, another exemplary solution extractionplant 400 suitable for use in processes 100 and 200 is illustrated.Solution extraction plant 400 comprises a first circuit 401 and a secondcircuit 402. Second circuit 402 may be the same or substantially similarto second circuit 302. First circuit 401 is similar to first circuit301, as both comprise four extractors (310, 320, 330, and 340) and twostripping units (350 and 360). However, the location of stripping unit450 of first circuit 401 differs from the location of stripping unit 350of first circuit 301.

As illustrated in FIG. 4, stripping unit 360 of first circuit 401receives first loaded organic stream 114 and lean electrolyte 108, andproduces first circuit enriched electrolyte stream 162 and barrenorganic stream 448.

Extractor 340 of first circuit 401 is configured to receive barrenorganic stream 448 and second circuit raffinate 186, and produceslow-grade raffinate 146 and a partially loaded organic stream 438.Extractor 330 is configured to receive partially loaded organic stream438 and second circuit raffinate 176, and produces high-grade raffinate136 and a loaded organic stream 424.

Stripping unit 450 of first circuit 401 is located between extractors320 and 330. Stripping unit 450 receives partially loaded organic stream424 and a raffinate 426, and produces a barren organic stream 428 and anenriched electrolyte 463. Enriched electrolyte 463 can be combined withfirst circuit enriched electrolyte 162, if desired. Barren organicstream 428 is forwarded to extractor 320, which produces raffinate 426and partially loaded organic stream 118.

With initial reference to FIG. 5, yet another exemplary solution plant500 suitable for use in processes 100 and 200 is illustrated. Solutionextraction plant 500 comprises a first circuit 501 and a second circuit502. First circuit 501 may be the same or substantially similar to firstcircuit 301 of solution extraction plant 300. Second circuit 502 issimilar to second circuit 302, and further comprises an additionalstripping unit 592. In such configurations, lean electrolyte 112 iscontacted with a partially stripped organic stream 598 in stripping unit592, producing an intermediate electrolyte 596 and a barren organic 588.Extractor 380 of second circuit 502 is configured to receive barrenorganic stream 588 and LGPLS stream 106, and produces partially loadedorganic stream 178 and second circuit raffinate 186.

Stripping unit 390 of second circuit 502 produces second circuitenriched electrolyte 192 and partially stripped organic stream 598 bycontacting the intermediate electrolyte 596 with loaded organic stream174. Although two stripping units are illustrated in second circuit 502,the use of any suitable number of stripping units in second circuit 502is within the scope of the present disclosure.

The present disclosure illustrates a number of exemplary solutionextraction plants comprising a first circuit and a second circuit influid communication with each other. Although the illustratedembodiments disclose particular combinations of first circuits (such as301, 401, and 501) and second circuits (such as 302, 402, and 502), anyfirst circuit and second circuit may be used together in a solutionextraction plant. Stated another way, any combination of circuits (suchas first circuit 401 and second circuit 502) is within the scope of thepresent disclosure.

Referring again to FIG. 1, in an exemplary embodiment, metal recoveryprocess 100 further comprises primary metal recovery step 50, in which asolution containing a sufficiently high amount of primary metal isforwarded to a process to extract the primary metal from the solution.For example, first circuit enriched electrolyte 162 and/or secondcircuit enriched electrolyte 192 may be forwarded to further metalrecovery processes. In accordance with various aspects of theembodiments, step 50 may comprise any metal recovery process, forexample, electrowinning, sulphidation, precipitation, ion exchange orany other process suitable for recovery of metals. Primary metals to berecovered may include copper, silver, platinum group metals, molybdenum,zinc, nickel, cobalt, uranium, rhenium, rare earth metals, and the like.By way of an example, step 50 may comprise an electrowinning circuitsuitably designed to carry out any electrowining process capable ofproducing a metal cathode product. However, any metal recovery processwhich results in a relatively pure metal product is within the scope ofthe present disclosure.

With continued reference to FIG. 1, an exemplary secondary metalrecovery step 60 includes recovering metal from a low-grade raffinate.In various exemplary embodiments, step 60 may comprise any metalrecovery process such as, for example, electrowinning, sulphidation,precipitation, ion exchange, cyanidation, or any other process suitablefor recovery of secondary metals. Further, as discussed in some detailbelow, in various exemplary embodiments, precipitation processes areused, thus making it advantageous to have low concentrations of primarymetals in low-grade raffinate 146. Additionally, in various exemplaryembodiments, secondary metals to be recovered in step 60 may include,silver, platinum group metals, molybdenum, zinc, nickel, cobalt,uranium, rhenium, rare earth metals, and the like.

As mentioned above, the quality of metal-bearing material 101 can varywidely over the course of a metal recovery process 100. Due to thisvariation, both primary and secondary metal recovery processes canevidence losses in efficiency and overall processing yields. One reasonfor these losses is the inability to control and tune the quality andcomposition of low-grade raffinate 146 from the step 40. For example,low-grade raffinate 146 may be subjected to a selective precipitationprocess wherein all metal ions except for those of the secondary metalto be recovered such as, for example, cobalt, are eliminated from thelow-grade raffinate 146 by precipitating them as solids. Theseprecipitated primary metal solids may be recycled to step 20. Theseprecipitated solids may have a high probability of being renderedunrecoverable, depending on the precipitating mechanism employed. In theinstance where there is high primary metal concentration in low-graderaffinate 146, the amount of precipitated primary metal solids recycledto step 20 may increase. This increase in precipitated metal solids maylead to process inefficiencies due to high circulating loads in varioussteps 30.

Similarly, the inability to control and tune the quality andconcentration of low-grade raffinate 146 directly affects the costsassociated with step 60. For instance, low primary metal quality andconcentration in low-grade raffinate 146 may require less reagent toeffect precipitation (operating cost savings). Thus smaller equipmentcan be used to recycle the copper precipitate (capital cost savings).

Various embodiments of the present metal recovery process advantageouslyallow for control and tuning of the low-grade raffinate 146. Moreover,step 40 may allow for control and tuning of low-grade raffinate 146 byadjustment of parameters such as, for example, the barren organic flowrate, reagent content, feed material flow rate, and/or any combinationsthereof. Additionally, in various exemplary embodiments, the overallefficiency of the metal recovery process may be influenced by blendingthe primary metal solids precipitated from the low-grade raffinate withhigh-grade raffinate prior to recycling to the reactive process step.

By making any of these adjustments to control and tune the quality andconcentration in the low-grade raffinate, the low-grade raffinate shouldpreferably contain very limited amounts of the primary metal, whichallows for efficient secondary metal processing. Additionally, the metalrecovery process and solution extraction system described above allowsplant operators to maintain a substantially controlled metalconcentration in the HGPLS stream, LGPLS stream, and the raffinatestreams.

As discussed above, in various embodiments, the flow rate andconcentration of the barren organic flow containing a metal-specificextraction reagent can be altered based on the incoming metal orequality to maintain a constant concentration of metal in the low-graderaffinate, allowing for efficient secondary processing of other metals,including but not limited to cobalt recovery. In an aspect of theseembodiments, because both the HGPLS and LGPLS streams are treated in onefacility, the metal content of the LGPLS may be controlled and heldconstant by adjusting LGPLS rate according to grade, with the excessbeing blended with the HGPLS.

The present disclosure allows the extraction circuit for the primarymetal value to be tuned and optimized, both in terms of metallurgicalperformance and capital and operating costs. There is a trade offbetween achieving optimum metallurgical performance and minimizing thecapital costs of the operating facility. The decisions made regardingthis trade off are based on the performance and cost of themetal-specific extraction reagent employed as well as the chemistry ofthe pregnant leach solution streams to be treated. For example, the useof a metal-specific extraction reagent which exhibits rapid extractionkinetics may minimize the number of sequential extractors needed toachieve a satisfactory level of metal recovery. The presence of iron,manganese, or chloride in the pregnant leach solution streams mayrequire the use of a wash stage prior to stripping. The number andplacement of stripping units may be decided based on the strippingkinetics of the extraction reagent as well as its maximum metal loadingcapacity. Accordingly, various configurations are within the scope ofthe present disclosure.

It is believed that the disclosure set forth above encompasses at leastone distinct invention with independent utility. While the invention hasbeen disclosed in the exemplary forms, the specific embodiments thereofas disclosed and illustrated herein are not to be considered in alimiting sense as numerous variations are possible. The subject matterof the invention includes all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/orproperties disclosed herein and their equivalents.

The method and system described herein may be implemented to recovercopper and other metals in a controlled manner. Other advantages andfeatures of the present systems and/or methods may be appreciated fromthe disclosure herein and the implementation of the method and system.

1. (canceled)
 2. A method of extracting a metal value comprising:extracting, using a first circuit of a solution extraction plant, afirst electrolyte; and extracting, using a second circuit of thesolution extraction plant, a second electrolyte, wherein the firstcircuit comprises at least two first circuit extractors and at least onefirst circuit stripping unit, wherein the second circuit comprises atleast two second circuit extractors and at least one second circuitstripping unit, wherein the first circuit and the second circuit are influid communication.
 3. The method of claim 2, further comprisingforwarding a first electrolyte to a primary electrowinning unit.
 4. Themethod of claim 2, further comprising forwarding a second electrolyte toa second electrowinning unit.
 5. The method of claim 2, wherein thefirst electrolyte is a rich electrolyte.
 6. The method of claim 2,wherein the second electrolyte is a rich electrolyte.
 7. The method ofclaim 2, further comprising extracting, using the first circuit of thesolution extraction plant, a first circuit raffinate.
 8. The method ofclaim 2, further comprising extracting, using the second circuit of thesolution extraction plant, a second circuit raffinate.
 9. The method ofclaim 8, further comprising forwarding the second circuit raffinate tothe first circuit.
 10. The method of claim 8, further comprisingextracting, using the second circuit of the solution extraction plant, asecond second circuit raffinate.
 11. The method of claim 10, furthercomprising forwarding the second second circuit raffinate to the firstcircuit.
 12. The method of claim 2, further comprising extracting, usingthe first circuit of the solution extraction plant, a high-graderaffinate.
 13. The method of claim 2, further comprising forwarding alean electrolyte to the at least one first circuit stripping unit or theat least one second circuit stripping unit.
 14. The method of claim 2,wherein the metal value comprises copper.
 15. A method of extracting ametal value comprising: forwarding a first electrolyte to a primaryelectrowinning unit; and forwarding a second electrolyte to a secondelectrowinning unit, wherein the first electrolyte is produced by afirst circuit of a solution extraction plant, wherein the secondelectrolyte is produced by a second circuit of the solution extractionplant, wherein the first circuit comprises at least two first circuitextractors and at least one first circuit stripping unit, wherein thesecond circuit comprises at least two second circuit extractors and atleast one second circuit stripping unit, wherein the first circuit andthe second circuit are in fluid communication.
 16. The method of claim15, further comprising extracting, using the first circuit of thesolution extraction plant, a first circuit raffinate.
 17. The method ofclaim 15, further comprising extracting, using the second circuit of thesolution extraction plant, a second circuit raffinate.
 18. The method ofclaim 17, further comprising extracting, using the second circuit of thesolution extraction plant, a second second circuit raffinate.
 19. Themethod of claim 17, further comprising forwarding the second circuitraffinate to the first circuit.
 20. The method of claim 18, furthercomprising forwarding the second second circuit raffinate to the firstcircuit.